Electric incandescent lamp



Aug. 22, 1939. E. FRIEDERICH a-rAL H 2,170,683

ELECTRIG INCANDESCENT LAMP.

Filed March 18, 1936 CONN/M5 RARE NEMLL/C OXIDE.

GONTAM/S OXYGEN.

Inventors: Ernst, Frieder-ich, v WiIFried Meyer",

Their" Attorneg.

: Patented Aug. 22, 1939 a I UNITED STATES" PATENT OFFICE ELECTRIC INCANDESCENT Ernst Friederich, Beriin-Charlottenburg, and Wilfried Meyer, Birkenwerder, near Berlin, Germany, assign'ors to General Electric Company, a corporation of NCITYOI'K Application March 18, 1936, Serial No. 69,591

In Germany April 30, .1935.

Claims. (01. 176-19) Our invention relates to electric incandescent is possible to proceed independently of the origilamps and more particularly to incandescible nal grain size of the materials and a large numbodies or filaments for such lamps. her of filaments may be manufactured having the In the conventional incandescent lamps having same eTectrica-l properties. Instead of magnesi tungstenfilaments, the current densities are much um oxide, other insulating oxides may be used,

5 higher upon switching in of thelamps than they such as aluminum oxide, chromium oxide, manare duringthesubs'equent normal burning of the ganese oxide, etc. As a result of the mixing or lamps. This is not harmful to the incandescent solution, the specific resistivity of the filament lamp itself since the filament is not heated to is-so increased that filaments may be produced a temperature in excess of that attained during -having a comparatively large diameter, that is, m

the normal burning of the lamp. However, this a comparatively high thermal capacity for a characteristic may be harmful, for instance, in given length. cases where the lamps are operated in series with Incandescibie bodies made of oxides and oxide other current consuming devices, the starting mixtures and of considerable thickness have been time of which exceeds that of the filament of the proposed heretofore for usein the so-called Nemst lamp. In such cases the voltage drops a few lamp. These bodies, however, have the disadseconds, or even-minutes, after the switching in vantage that they must'be preheated by a special of the lamp is frequently greater than the drop appliance in order to render them conductive. existing during the normal operation of the lamp, The incandescent bodies according to the present thereby causing a much higher watt consumption invention are conductive at low voltages and have, and considerable overheating which, in turn, unlike the Nernst lamp, a purely electronic conshortens the ,life of the lamp. ductivity. Y These bodies must be operated in an An object of our invention is to provide an evacuated spac ,f Otherwise y wou d oxidize incandescibie body or filament having a higher into non-conducting Poorly conducting Oxides. thermal capacity, that is, a longer heating period such as H02, (205, NbzOs, VaOa. than that of the ordinary tungsten filament and It has been found that at very high temperaof the other filaments which have since become tures, above, say 1200 C., the loosening of the known. Another object is the provision of a lattice system of oxidic bodies becomes so prolamp' which may be used in series with other nounced that even those bodies which at room power consuming devices, such as lamps for the temperature have a perfect electronic conducillumination of dials, of instruments, lamps ,--for tivity are partly electrolytically decomposed at microscopes, etc., where tungsten filament lamps the said higher temperatures. It has been obmay not be used unless special protective measserved that these oxidic solutions retain their ures are taken. electronic conductivity completely, even at tem- The drawing is a per pective view 01' an inperatures up to 2000 C. and more, when a small 35 candescent a p Comprising our invention partial pressure of oxygen is provided. Of course Referring to the drawing, the lamp comprises t partial pressure of oxygen must be slight 319155 u or envelope In having P311 or that the incandescible body will not oxidize to a f F therethmugh d higher state of the oxide. It is particularly adportlng-an mcandescible body or filament i2 comvantageous to the envelopes or bulbs of the prising me metal! lamps with nitrogen to which is added 0.001% to According to our invention, a number of sub- 05% of oxygen other inert gases may of course 2:22:55 iggfi ggf g g g gfig g?i g gzf' be used in place of nitrogen. Hydrogen may also er vanadium oxides, niobium oxides and titanium be as gas fiumg when the ii i I oxides. Some of the said lower'oxides, especially homes are made of uranium dioxide and h the lower oxides of vanadium and niobium case the slightly oxidizing atmosphere is crewell as those of titanium, have such a low specific ated by adding water vapor hydlfogenresistivity that incandescible bodies made there- The lamps my also be made wlthout an inert w from may have the thickness of a metal thread. gas and having. only P content- These oxides are preferably mixed with insulaincandescibl? homes y b de in the tors which permit a complete or partial solution conventional m nn r by pr br x r l n of the conducting ingredient in the non-conductwith or without binders, and by baking at high ing vehicle, such as a low titanium oxide in magtemperatures. They may also be provided with nesium oxide. Because of the mutual solution, it coatings of selectively radiating or poorly radiattures of the order of 2000 C. but insuflicient to cause conversion of said rare'metallic oxide to a higher form of non-conductive oxide.

2. An electric incandescent lamp comprising an envelope, an incandescible body in said envelope comprising a rare oxidizable metallic oxide which is conductive at ordinary temperatures, and an atmosphere comprising an inert gas and a small amount of oxygen in said envelope, the amount of oxygen being sufiicient to cause said incandescible body to retain its electronic conductivity at temperatures of the order of 2000 C. but insufficient to cause conversion of said rare metallic oxide to a higher form of non-conductive oxide.

3. An electric incandescent lamp comprising an envelope, an incandescible body in said envelope comprising almixture of a rare oxidizable metallic oxide which is conductive at ordinary temperatures and a non-conductive refractory metallic oxide, and an atmosphere comprising a'small amount of oxygen in said envelope, the amount of oxygen being sufiicient to cause said incandescible body to retain its electronic conductivity at temperatures of the order of 2000" C. but insufii'cient to cause conversion of said rare metallic oxide to a higher form of non-conductive oxide.

4. An electric incandescent lamp comprising an envelope, an incandescible body in said envelope comprising a mixture of a rare oxidizable metallic oxide which is conductive at ordinary temperatures and a non-conductive refractory metallic oxide, and an atmosphere. comprising an inert gas and a small amount of oxygen in said envelope, the amount of oxygen being sufficient to cause said incandescible body to retain its electronic conductivity at temperatures of the order of 2000 C. but insuflicient to cause conversion of said rare metallic oxide to a higher form or non-conductive oxide.

5. An electric lamp comprising a sealed enve- -lope and a filament in said envelope consisting ment to retain its electronicconductivityattem-v peratures of the order of 2000f"C.'butlnsi1flicient to cause conversion of said first-me'ntion oxide to a higher form of non -conductiv'e oxi'de 1 f ERNST F IEDERiC F E 

